Airgun piston

Abstract: Improvements in air guns of the hinged barrel type, with a barrel (28) acting as a lever arm of a hinged leverage (5) to compress a spring (4) attached to an axially movable piston (1), tightly inserted in a compression chamber (2), with thrusting means (5) associated to said piston for compressing said spring and a safety catch (6) which locks said piston in a spring compressed position suitable for shooting. The improvements consists in producing said piston (1) in a tubular shape moulded in plastic material, including tightness means (8,11), a supplementary element resistant to wear providing a link between said piston, said thrusting means (5) and said safety catch (6), and a supplementary weighty element (10), integral to said tubular piston. A casing (27) completely covers the barrel (28) body excepting its front and rear ends and each of the two lateral sides of said rear end (29) of said casing (27), bear ample recesses (31), apt to snugly fit, in the closed position of the gun, upon corresponding projecting ridges (32) of the inner wall of each one of the limbs of a fork (30a) pertaining to a one-piece body extending rearwards thereby forming said compression chamber.

Description: Technical field The invention relates to improvements in air guns mainly of the hinged barrel type where the barrel acts as a lever arm of a hinged leverage operable to compress the spring of a compression chamber mounted on the buttstock body of the gun, including an axially movable piston, located inside said compression chamber associated to the gun body, said piston being in contact with said loading spring and comprising means, generally in a material different from that of the piston, adapted to secure the tightness between its external surface and the internal wall of the compression chamber, said piston being further associated with thrusting means, in order to compress said spring, as well as to a safety catch which locks the piston in a spring compressed position suitable for shooting. The preamble of claim 1 is based on EP-A-0 467 819. Background of the invention An example of a state of the art air gun is disclosed in EP-A-467819 of same inventor wherein the invention mainly consists in a particular embodiment of a fork-shaped piece, hinged on the barrel, an its locking on the compression chamber end, as well as the features of a casing of plastics material moulded on the barrel, with a back part thereof pivotally hinged with a fork member constituted by a one-piece body moulded as well in plastics material, with a rearward extension which is integral with the front part of said compression chamber, there being an axial passage extending through said rearward extension for the passage of the compressed air. Disclosure of the invention The invention is defined in claim 1. The dependent claims define preferred embodiments. It is still with the aim of reducing the cost of manufacture of said guns, that the inventor sought to improve the production of some parts of the gun reforming several aspect which essentially affect: the piston, which is still in metal, and of its tightness means, with respect to the compression chamber which is generally constituted by O-rings located within annular grooves on the piston external surface, or alternatively by nozzle-shaped joints (see GB-A-2173287) socketed on the front end of said piston and whose production cost is very high; the tightness of said guns because, in all the cases when using additionally parts of the O-ring type or nozzle-shaped joint, the air can pass through both sides thereof, on one hand, through its surface in contact with the compression chamber and, on the other hand, through its surface in contact with the piston recess; the means for alignment of the barrel with an axial passage for the outlet of the compressed air in the closed position of the gun; the one-piece body whose front part forms the fork for the hinged connection of the barrel, said one-piece body having now its functions extended; the sealing means between the rear end of the barrel and said axial passage for the compressed air. Additionally metallic pistons of the referred type comprise a lengthwise slot serving for the connection of the thrusting means, designed to compress the piston spring and for the inclusion of the safety catch, associated to the trigger, which locks the piston at a spring compressed position. Said slot sustains significant frictions and impacts so it is characterized by its great resistance to wear. GB-A-937 658 discloses a piston of this type comprising a tubular body formed from a sheet metal blank with a lateral slot 15 in which the cocking lever of a gun action can slide and at the rear end of this slot a portion 16 is turned down slightly to provide an abutment for engagement by the end of the lever for moving the piston for cocking the gun. The tubular piston has anchored to its front end a buffer for absorbing schock when the assembly strikes the end of the cylinder of a gun on firing. To cut the piston cost, a first attempt of the inventor consisted in producing it in plastic material incorporating a recess for the thrusting means and the safety catch. But even the harder plastic materials (regardless of their high cost incompatible with the aim sought) did not resist the stresses due to the repeatedly action of said thrusting means and said safety catch. Therefore is with the aim to cut the cost of the assembly "piston-sealing gasket-recess" while preserving the function and accurateness characteristics of the parts involved in these modifications under consideration, that the inventor conceives a piston: produced in plastic material, moulded with the shape of a tubular body, closed at one end by a front wall, which includes the tightness means between the body of said piston and the compression chamber also shaped by said molding operation; which includes a supplementary plate having a great resistance to wear providing a connection between said plastics piston body, the thrusting means and the safety catch; comprising a high density supplementary element, secured inside said tubular piston, adapted to provide the piston with an overall weigh conform to the functional working inertia compatible with the kind of gun used. Also characteristic of the invention is the fact that the one-piece body constituting the fork for the hinged connection with the barrel, made of moulded plastics material, extends itself rearwards with a tubular shape so as to form the compression chamber itself, and from said tubular part an appendage in the shape of a planar member extends laterally and allows to fix the firing mechanism, and more specifically the piston-spring assembly loading, locking and releasing means. Said fork has a flat bottom, and on the inner faces of its two limbs there are directly opposed projecting ridges which provide a notably elongated double seat, on which projecting ridges will snugly fit, in the closed position of the gun, ample recesses of adequate configuration made at both sides of a rear part of the barrel casing. Said seat-stop means have been adequately sized (with a considerable length) in order to efficiently distribute and/or absorb the impact stress, so that they constitute an efficient alternative to the half-round stop described in the above-mentioned EP-A-467819, and a notable improvement in respect with the conventional stepped positioning stops. The above and other objects, advantages and features of the present invention will become more apparent from the following description of a preferred embodiment thereof. Brief description of the drawings The invention will now be described in detail with reference to the accompanying drawings wherein: Fig. 1 is a partially cut perspective view, of the piston associated to its supplementary elements (plate and rod); Fig. 2 is an external plan view of the piston which evidences a housing for the supplementary plate; Fig. 3 is a partial perspective view of the piston associated to a supplementary plate provided with a different locking means; Fig 4 is a partially cut overall view showing the piston, the compression chamber, a part of the gun body, such as a rifle, and the different parts with which they are linked with a widening (A) of the piston end evidencing the tightness means. Figure 5 is a partial perspective view of the two parts constituting the gun in question, i.e. the barrel body and the fork, in an uncoupled state. Figure 6 shows a cross-sectional detail of the same gun, with its parts coupled and along section line VI-VI in figure 5. Figure 7 is an enlarged scale view in partial longitudinal section of the rear part of the barrel body. Figures 8 and 9 are two schematic views showing the relative arrangement of the two parts constituting the gun in firing position (figure 8) and in open position (figure 9) respectively. Figure 10 is a longitudinally sectional view showing a one-piece body made according to the invention and integrating the barrel coupling fork, the compression chamber and a support for the firing mechanism of the gun. Detailed description The gun illustrated in the drawings, such a rifle, comprises a piston 1, axially movable, located inside a compression chamber 2 linked to the gun body 3, said piston being in contact with a loading spring 4 and comprising means 8 adapted to secure the tightness between the piston external surface and the internal wall of the chamber 2, said piston being associated to thrusting means 5, of the hinged push-rod type which can compress said spring, as well as a safety catch 6 which locks the piston to the spring compressed position suitable for shooting. The piston is made of plastic material, moulded in a tubular configuration 1, closed at one end by a front wall 7 which includes the tightness means 8 shaped by the same molding operation. The link between the piston and the thrusting means (5) and the safety catch (6) is achieved through a supplementary element (9), having a great resistance to wear. The interior of the tubular body (1) houses a great density supplementary element (10), adapted to provide the piston with an overall weigh according to the functional working inertia needed. The tightness means 8 is made up, on the piston 1 front end, with the shape of a tightness lip constituted by a flared peripheral part 8 and an annular recess 11, made on the front wall 7, adjacent to said flared part. The supplementary element having a great resistance to wear is produced from a plate 9 which comprises a lengthwise slot 12, in which the thrusting means 5 is movable, said slot terminating, at one end, by a lateral extension 13 adapted to house the safety catch 6; said plate being backed on the bottom of the housing 14 pertaining to the piston lateral surface and whose depth is equal to the plate width so that the external surface of this later is at same level as the piston external surface; said plate comprising means for locking it to the housing 14. The means for locking the plate 9 to the housing 14 is achieved (see Fig. 1) through a bent lug 15 which goes to be housed within a suitable slit 16 of the piston 1. Said locking means can also be achieved with a stud 17 passing through a hole 18 made in the plate 9 and which goes to be inserted within a hole 19 pertaining to the piston 1 body (see Fig. 3). The plate 9 comprises, on its periphery, a plurality of protruding parts 20, adapted to be assembled in a plurality of housings 21, having related shapes, leading to the housing 14. The great density supplementary element is constituted by a rod 10, axially arranged, integral with the piston body 1. The rod 10 is made integral with the piston body 1, during the molding operation, by means of its end 22 which comprises peripheral striations 23 and a notch 24. The supplementary element 9 and the high density supplementary element 10 can be made as a single body supplementary element. The gun includes a trigger 25 which operates the safety catch 6 by means of a safety counter-catch 26 . According to figures 5 to 10, the air gun of the hinged barrel type of the present invention belongs to the type where the barrel acts as a lever arm of a hinged leverage operable to compress the spring of a compression chamber mounted on the buttstock body of the gun and is constituted by a casing 27 of plastics material moulded on said barrel 28 and comprising a rear part 29 hinged around a pin 34 with a one-piece body 30 also made of plastics material integrating a fork part 30a with projecting ridges 32 on the inner walls of its limbs, said part 30a extending rearwards thereby forming a cylindrical cavity 30c (or compression chamber) which is intended to house a piston such as the tubular one in plastic material previously described, and from said cavity 30c a lateral extension 30d in the shape of a planar member extends besides towards the outside for the support of the firing mechanism of the gun. An axial passage 30b in alignment with the axial tubular passage 28a of the barrel 28 in the closed position of the gun, communicates said cavity 30c with the bottom 47 of the fork 30a, all this according to a structure such as the one described in the above-mentioned EP-A-467819. In the present invention the rear end 28a of barrel 28, as opposite to what happens in the embodiment of the above-mentioned EP-A-467819 (projecting rear portion of said barrel acting as a closing stop with regard to a reciprocal half-round stop carried out in the fork), flushes, i.e. is coplanar, with the rear face of said end part 29 of casing 27, surrounding it completely. Said rear end part 29 has in its turn in its lateral sides and adjacent to its lower side respective recesses 31 substantially elongated in the direction of the barrel and snugly fitting, when the gun is in the closed position, upon as many projecting ridges 32 existing on the inner walls of the limbs of the fork 30a, there being in such a position a perfect alignment of said tubular passage 28a with passage 30b, this latter ending in the flat bottom 47 of the fork. By means of this embodiment, said projecting ridges 32 provide, as has been said before, a double seat at both sides of rear part 29 of the casing or barrel body 27, and because of their considerable length they provide an adequate stop and positioning means (furnishing a substantial distribution and absorption of the impact stress) which guarantees an exact alignment, in firing position of the gun, of said passages 28a and 30b. It is as well essential that projecting ridges 32 present at least a plane 32a at right angles to the inner wall of the fork and oriented parallel to the axis of axial passage 30b in a preferred embodiment. Said projecting ridges 32 present as well two planes 32a, 32b which are at right angles to the inner wall of the fork, intersect each other at an angle of slightly less than 90° and have their frontal intersecting angle edge 32c rounded. Finally and in correspondence with what has been said above, recesses 31 present two planes 31a, 31b which are at right angles to the major face of the recess itself and intersect each other at a solid angle 31c of slightly more than 90°, one 31a of said planes being in a preferred embodiment oriented parallel to the axis of barrel 28. Figures 8 and 9 show how the forward 32c and rearward 31c solid angles of projecting ridges 32 and recesses 31 allow the closing and opening of the gun without contact between said parts. It can also be seen in these figures that there is a little cutoff 35 at the back of part 29 which serves to facilitate the tilting of the barrel body without an appreciable friction against the flat bottom 47 of fork 30a. As can be seen in figures 5 and 6, in order to guarantee a tight sealing in the closed position of the gun between the inlet of tubular passage 28a at the back end of the barrel 28 and passage 30b it has been foreseen that said back end 28a of the barrel 28 is surrounded by a ring-shaped groove in which a sealing ring 33 nests and projects slightly from the back face of said rear part 29 of casing 27. Other elements appearing in the figures, of conventional type, and not having been described are the following: holes 36 directly opposed in the limbs of fork 30a for the hinged connection with the rear part 29 of the barrel body by means of pin 34 mounted through hole 37 of said part 29; recess 38 housing a closure catch 39 with the mutually hinged parts 27, 29 and 30 in the firing position of the gun; holes in the lateral extension 30d in the shape of a planar member: 49 for the pin-jointing of the trigger, 40 for the pin-jointing of a pawl associated to the piston (not shown) of the compression chamber, 41 for the fitting up of a counter-pawl, and 42 for the fitting up of a trigger safety catch; holes 43, 44 for the fitting up of centring elements, opening 45 for the passage of a leverage spring, and hole 46 for the fitting up of a pin associated to a leverage connecting rod, all of them made also in said extension 30d.

Claims: An air gun of the hinged barrel type, with a barrel (28) acting as a lever arm of a hinged leverage aimed to compress a spring (4) attached to an axially movable piston (1) closed at one end by a front wall (7) tightly inserted in a compression chamber (2) mounted on the buttstock body of the gun, including thrusting means (5), of the hinged push-rod type, associated to said piston (1) for compressing said spring and a safety catch (6) which locks said piston in a spring compressed position suitable for shooting characterized in that the gun comprises: a tubular piston (1) moulded in plastic material; a tightness lip (8) shaped by molding at said front wall (7) of said piston closed one end; a plate (9) having a great resistance to wear providing a link between said piston, said thrusting means (5) and said safety catch (6); a rod (10) located inside said tubular piston, adapted to provide the piston with an overall weigh conform to the functional working inertia needed. An air gun as claimed in claim 1, characterized in that said tightness lip (8) made up on said piston closed front end, is constituted by a flared peripheral part and an annular recess (11) on said front wall (7) adjacent to said flared part. An air gun as claimed in claim 1, characterized in that said plate (9) includes a lengthwise slot (12), in which an end of said thrusting means (5) is movable, said lengthwise slot (12) terminating at one end, by a lateral extension (13) adapted to house a safety catch (16); said plate (9) being backed on the bottom of a housing (14) pertaining to a piston lateral surface and whose depth is equal to the plate (9) width, and said plate (9) comprising means for locking it to said housing. An air gun as claimed in claim 3, characterized in that said means for locking said plate (9) to said housing (14) is achieved through a bent cross pin (15) housed within a suitable slit (16) of an external wall of said piston. An air gun as claimed in claim 3, characterized in that said means for locking said plate (9) to said housing (14) is achieved through a stud (17) passing through a hole (18) made in said plate (19) and which goes to be inserted within a hole (9) pertaining to an external wall of said piston. An air gun as claimed in claim 3, characterized in that said plate (9) comprises, on its periphery, a plurality of protruding parts (20), adapted to be assembled in a plurality of housings (21), of related shapes, adjacent and leading to said housing (14). An air gun as claimed in claim 1, characterized in that said rod (10) is axially arranged, integral with said piston (1) body. An air gun as claimed in claim 7, characterized in that said rod (10) is made integral with said piston (1) body, during the molding operation, by means of one end thereof which comprises peripheral striations (23) and a notch (24). An air gun as claimed in claim 3, characterized in that said supplementary element (9) providing a link between said piston (1), said thrusting means (5) said safety catch (6) and said high density supplementary element (10) can be made integral as a single supplementary element. An air gun according to claim 1, said gun further including: a casing of plastics material moulded on said barrel, with a rear part pivotally hinged with a fork constituted by a one-piece body, moulded as well in plastics material; a rearward extension of said fork which is integral with the front part of said compression chamber; an axial passage extending through said extension for the outlet of the compressed air; a casing (27) which completely covers said barrel (28) body excepting its front and rear ends, the latter (28a) being coplanar of said casing (27); and ample recesses (31) on each of the two lateral sides of said rear end (29) of said casing (27), adjacent to its lower side, substantially elongated in the longitudinal extension of said barrel (28) itself, said recesses (31) being apt to snugly fit, in the closed position of the gun, upon corresponding projecting ridges (32) of the inner wall of each one of the limbs of said fork (30a) with a perfect alignment of said barrel (28) of the gun with said axial passage (30b) for the outlet of the compressed air, and with said rear end (29) of the casing (27) in contact with a flat bottom (47) of said fork. An air gun as claimed in claim 10, characterized in that said projecting ridges (32) have at least a plane (32a) at right angles to the inner wall of the fork (30a), narrow and elongated and substantially oriented in parallelism to the axis of said axial (30b) passage for the outlet of the compressed air. An air gun as claimed in claim 10, characterized in that said projecting ridges (32) have two planes (32a, 32b) which are at right angles to the inner wall of the fork, intersecting each other at an angle of slightly less than 90° and have their frontal intersecting angle (32c) edge rounded. An air gun as claimed in claim 10, characterized in that said recesses (31) have two planes, which are at right angles to a major face of the recess itself and intersect each other at a solid angle (31c) of slightly more than 90°, one of said planes being oriented parallel to the axis of said barrel. An air gun as claimed in claim 10, characterized in that: said one-piece body integrating said fork (30a) with said projecting ridges (32) on the inner walls of its limbs extends rearwards thereby forming a cylindrical cavity (30c) which is intended to house a piston, and a lateral extension (30d) in the shape of a planar member outwardly extends from said cavity (30c) for supporting of the firing mechanism of the gun. An air gun as claimed in claim 10, characterized in that said back end (28a) of said barrel (28) is surrounded by a ring-shaped groove, with a sealing ring (33) nested within which slightly projects from the back face (29) of said casing (27).

Inventors: CASAS-SALVA FRANCISCO, CASAS-SALVA, FRANCISCO
Applicants: GAMO IND SA, INDUSTRIAS EL GAMO, S.A.
Application year: 1994
Main classification: F41B11
IPC codes: F41B11